Solve for $x$ and $y$ using substitution. ${-x-3y = -1}$ ${x = -y+3}$
Answer: Since $x$ has already been solved for, substitute $-y+3$ for $x$ in the first equation. ${-}{(-y+3)}{- 3y = -1}$ Simplify and solve for $y$ $y-3 - 3y = -1$ $-2y-3 = -1$ $-2y-3{+3} = -1{+3}$ $-2y = 2$ $\dfrac{-2y}{{-2}} = \dfrac{2}{{-2}}$ ${y = -1}$ Now that you know ${y = -1}$ , plug it back into $\thinspace {x = -y+3}\thinspace$ to find $x$ ${x = -}{(-1)}{ + 3}$ $x = 1 + 3$ ${x = 4}$ You can also plug ${y = -1}$ into $\thinspace {-x-3y = -1}\thinspace$ and get the same answer for $x$ : ${-x - 3}{(-1)}{= -1}$ ${x = 4}$